In recent years, various mobile types of cellular phones have been provided. A common type of cellular phone, is a foldable cellular that have excellent operability. The folding of the cellular phone can prevent erroneous operations of keys. FIG. 1 illustrates an example of a conventional foldable cellular phone.
As illustrated in FIG. 1 a foldable cellular phone 1 includes a display-side housing 2 and a keyboard-side housing 3 that are connected with a hinge 4. The cellular phone 1 can be used when the display-side housing 2 is opened with respect to the keyboard-side housing 3 around the hinge 4. When the cellular phone is not used, it may be carried so that the display-side housing 2 is folded on the keyboard-side housing 3. Further, within the hinge 4, there can be wiring that electrically connects the display-side housing 2 and the keyboard-side housing 3.
Conventionally, in such a cellular phone 1, the hinge 4 includes a mechanism in which a shaft and a bearing are combined, and a hard ABS resin material (Acrylonitrile-Butadiene-Styrene resin), or the like, have been used. However, it has been difficult for the hinge 4 having the conventional structure to obtain high reliability in view of impact resistance, being water-tight, and the like. For example, with the hinge 4 molded with resin, operation may cause cracks of the case.
Conventionally, a hinge structure has been disclosed in which the hinge is not formed in combination of the shaft and the bearing, but formed of a silicone-based soft resin or rubber having elasticity; and a folding is performed by flexibly deforming the hinge itself. The hinge structure can improve the structure being watertight and impact resistance.
However, in the hinge structure disclosed conventionally, since the soft resin or the rubber are elastically deformed when being folded, the elastic restoring force makes it difficult to maintain the display-side housing 2 and the keyboard-side housing 3 in a folded state, and thus there has been a problem of poor usability.
In recent years, cellular phones that can receive terrestrial digital broadcasting have been provided, and it is desirable that the hinge include a tilt function that can adjust an open angle of the display-side housing 2 with respect to the keyboard-side housing 3. However, there has been a problem in that a hinge formed of the soft resin and the rubber cannot satisfactorily address such a problem.